Holocene climate fluctuations in the Yangtze delta of eastern China and the Neolithic response

Abstract

Six major pollen-spore assemblage zones can be identified showing alternate warm and cool climate fluctuations on a millennial timescale. The early-Holocene optimum at c. 8000-7800 radiocarbon years BP, is marked by a large proportion of evergreen broad-leaf species in Zone I, suggesting the warmest/hottest climate setting of the Holocene. The mid-Holocene optimum ran from c. 7500 to 5000 BP (Zone III), during which many subtropical warmand wet-tolerant species represented by Castanopsis and Cyclobalanopsis glauca occurred, indicating the megathermal trend. The temperature then declined upcore in Zone IV accompanied by a high proportion of Pinus and Cupressaceae. A cooling event occurred at c. 4200 BP, as evidenced by Fagus and Potamogeton in the upper section of Zone IV. Pollen assemblages in Zones V-VI indicate a generally cooler temperature in the late Holocene with a high proportion of Gramineae, indicative of rice cultivation. Onset of the mid-Holocene optimum was associated with sediment deposition of the Holocene delta construction. This promoted the migration of Neolithic settlements onto the delta plain from highlands west of the study area. The cooling event recognized at c. 4200-4000 BP may have triggered the cultural ‘break up’ caused by the climatic transition from early warm-humid to a later cool-wet setting, and lake expansion caused by heavy precipitation.

The Checkered Prehistory of Rice Movement Southwards as a Domesticated Cereal—from the Yangzi to the Equator

“…By the time that rice cultivation was spreading into regions such as Vietnam and Taiwan (c.3,000 to 2,000 BC), the inner part of the Yangzi Basin had become locked into a cycle of wet rice intensification and geographic inertia that would have slowed down any inclination for migration on the part of the core populations themselves, unless adverse environmental conditions altered the situation drastically. There is indeed some evidence that stress factors might have afflicted lower Yangzi populations during the Maqiao phase between 1,900 and 1,200 BC (Chen et al 2005), but this seems a little late in time as an explanation for rice expansion, given that rice farmers had already been in Taiwan for about a millennium beforehand.…”

Holocene-aged sedimentary records of environmental changes and early agriculture in the lower Yangtze, China

“…Evidence from elsewhere in the lower Yangtze suggests that post-glacial warming led to a mid-Holocene climatic optimum, when temperatures were 2-4 1C warmer (Wang and Gong, 2000;Yi et al, 2003;Chen et al, 2005) and levels of precipitation were substantially higher than present -the latter due to an enhanced East Asia summer monsoon Steinke et al, 2006), and to the replacement of cool temperate forests by more thermophilous taxa (e.g., Liu et al, 1992;Chen and Chen, 1996;Chen et al, 1997;Yi et al, 2003). This replacement is in accordance with data from Guangfulin and Qingpu, although human activity could have been a factor, given a concomitant increase in charcoal, along with hydrological change: at Guangfulin, pollen from forest taxa, notably conifers and several temperate evergreen and deciduous taxa, is far lower in abundance than during the lateglacial, while pollen from more open types of vegetation (e.g., Poaceae) and freshwater wetland habitats (Cyperaceae and Typha) is much more common.…”

Environmental history, palaeoecology and human activity at the early Neolithic forager/cultivator site at Kuahuqiao, Hangzhou, eastern China

“…There are several published pollen profiles from the lower Yangtze region with which it can be compared Xu et al, 1996;Tao et al, 2005;Chen et al, 2005;Yi et al, 2006;Shu et al, 2007) as well as more general regional syntheses for east China (Liu, 1988;Sun and Chen, 1991;Ren and Beug, 2002;Zhang et al, 2005;Ren, 2007) and national climate records (Shi et al, 1993;Feng et al, 2006). The Hangzhou/lower Yangtze area lies near the boundary between the temperate broadleaf forest biome of northeast China and the sub-tropical evergreen forest biome of the southeast, and so the mixed deciduous/evergreen forests there are very sensitive to climate change due to shifts in the strength and influence of the summer monsoon (Yu et al, 2002;Morrill et al, 2003;Wang et al, 2005).…”

“…Climatic and sea-level fluctuations in the first half of the Holocene must have had major implications for the location of Neolithic settlements, their success and even survival in this area (Stanley and Chen, 1996;Chen et al, 2005Chen et al, , 2008Yu et al, 2000) as elsewhere in coastal eastern China (Jiao, 2006). With rising water tables and frequent flooding (Zhu et al, 2003) local topographic variability must have caused major differences in settlement potential over small spatial areas (Stanley and Chen, 1996;Zhang et al, 2004;Xin and Xie, 2006).…”